* <tr><td>{@code [a..b]}  <td>{@code {x | a <= x <= b}}<td>{@link Range#closed closed}
 * <tr><td>{@code (a..b]}  <td>{@code {x | a < x <= b}} <td>{@link Range#openClosed openClosed}
 * <tr><td>{@code [a..b)}  <td>{@code {x | a <= x < b}} <td>{@link Range#closedOpen closedOpen}
 * <tr><td>{@code (a..+∞)} <td>{@code {x | x > a}}      <td>{@link Range#greaterThan greaterThan}

 * rangeSet.add(Range.closedOpen(11, 15)); // disconnected range; {[1, 10], [11, 15)}
 * rangeSet.add(Range.closedOpen(15, 20)); // connected range; {[1, 10], [11, 20)}
 * rangeSet.add(Range.openClosed(0, 0)); // empty range; {[1, 10], [11, 20)}
 * rangeSet.remove(Range.open(5, 10)); // splits [1, 10]; {[1, 5], [10, 10], [11, 20)}
 * }</pre>
 *

      if (set.isEmpty()) {
        /*
         * The (tooLow + 1, tooHigh) arguments below would be invalid because tooLow would be
         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);
      set.add(tooLow);

      if (set.isEmpty()) {
        /*
         * The (tooLow + 1, tooHigh) arguments below would be invalid because tooLow would be
         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);
      set.add(tooLow);